Mechanics

KNOCK SENSOR

2000 Mercury Villager

Engine Mechanical problem
2000 Mercury Villager 6 cyl Front Wheel Drive Automatic 150000 miles

I am very discourages and frutstrated however I really need answers. Here goes
About 6 months ago I began having problems with my car skipping. I took it in to get the spark plugs and spark plug wires changed. After this, the skipping stopped for about 2 weeks then started again. My mechanic said this would be the spark plugs buy maybe the wires so I paid to have them replaced a second time. This helped for about 2 more weeks. The van starts skipping again, this time the check engine lights comes on and is flashing on and off. It does do it all the time only when the car is skipping/hesitating (btw the van is not skipping/hesitating all the time - only on occasion - maybe once every 2 to 3 days). I take the car in once again after the skipping causes the van to stall out. This time the mechanic calls me back and says the computer is reading bad knock sensor and that spark 5 is misfiring. He tells me that it is going to cost me close to $700.00 to replace the knock sensor HOWEVER this will not guarantee that the skipping/hesitations will stop. He explained that he was not sure how a " sensor" would cause the car's engine to skip.
So I take the van to another mechanic in hopes for a second opinion. He tells me the same thing.I can replace the knock sensor but it just doesnt make sense that a sensor would cause skipping or hesitation.
Frustrated and hopeless, I now take the van to a Ford dealership. They have my van for 2 weeks, they keep calling me telling me they cannot find out what is going on with the van. They hook it up to the computer and they said that spark 5 is misfiring and the knock sensor is bad, however let us keep looking becuase this just does not make sense. They told me that Nissan is actaully the company that made the Mercury Villager so they would need to research some more. They call me back and tell me that one of my spark plug wires has water in it and this is what is causing the misfire and the reason it took so long to find this is becuase the sparks are numbered backwards on the villager. I immediately asked them where is the water coming from cause I was concerned that I had a cracked head. They said there was no issue with the head, that my seal was bad on my hood and that is where the water was probably coming from (which made no sense to me because I park my van in a garage - it never sits in the rain). I pick the van up and it is running great! No skipping or hesitation and the check engine light is not on. I have the van for one month and then completely out of the blue driving down the road one day the van starts jerking like it has become possessed. It does this for about 2 miles and then completely stops. No lights are coming on or anything. Later that night, I get in the car, drive about 2 miles and the jerking starts again. So bad to the point of make lots of noises becuase it is skaking everything and everyone in the car. Again, no dash lights are flashing on or anything. I am scared at this point to drive the van so I pay to have it towed to a different mechanic. He calls me today and says the computer says the knock sensor is bad.I am so frustrated I do not know what to do.I tell him my whole story of what the other mechanics have said in the past about this not being a knock sensor problem and he says different. He says that it can cause the van to jerk. Can you please help me!
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Bobbijoscarboro
March 12, 2010.




Hello. Thanks for the donation. Much appreciated

The symptoms your describing sound exactly like a faulty MAF (mass airflow) sensor would cause. This should set it's own fault code. But not alway's?

TEST DG: KNOCK SENSOR (KS)
Diagnostic Aids
Perform this test only when directed by QUICK TEST. This test is intended to diagnose the following: Knock Sensor (KS)
Harness Circuit: KS
Powertrain Control Module (PCM)
To prevent replacement of good components, be aware the following non-EEC related areas may be at fault: Poor Fuel Quality
Ignition Timing
Engine Mechanical Condition
CIRCUIT PIN IDENTIFICATION
CircuitPCM Pin No. Wire Color
KS63White
GND45Black/Red

NOTE: Freeze frame data will not be stored in the ECM for the knock sensor. The MIL will not light for a knock sensor malfunction.

DTC P0325

DTC P0325 indicates that spark knock has occurred and knock sensor failed to detect. Possible causes for this fault are as follows: PCM not receiving signal.
Open or short in harness.
Faulty knock sensor.
Faulty Powertrain Control Module (PCM).
Turn ignition off. Disconnect PCM. Disconnect knock sensor in-line connector. Measure resistance of KS signal circuit (White wire) between PCM connector terminal No. 63 and KS in-line connector. Measure resistance of GND circuit (Black/Red wire) between PCM harness connector terminal No. 45 and KS in-line connector. If resistances are less than 5 ohms, go to next step. If resistances are more than 5 ohms, repair open in White or Black/Red wires. See Fig. 11. See CIRCUIT PIN IDENTIFICATION table.
Check KS Circuit For Short To Ground

Disconnect PCM. Disconnect KS in-line connector. Measure resistance of KS circuit between PCM connector terminal No. 63 (White wire) and GND terminal No. 45 (Black/Red wire). If resistance is more than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, repair short circuit in wiring.
Fig. 11: Identifying KS Sensor Connector Terminals
Courtesy of FORD MOTOR CO.
Check KS Circuits For Short To Power

Disconnect PCM. Disconnect KS in-line connector. Measure resistance of KS circuit between PCM connector terminal No. 63 (White wire) and VPWR terminals No. 66 and 97 (Black/White wires). Measure resistance between PCM connector terminal No. 63 (White wire) and KAPWR terminal No. 80 (Yellow wire). If each resistance measurement is more than 10 k/ohms, go to next step. If each resistance measurement is less than 10 k/ohms, repair short circuit in wiring.
Check Resistance Of KS

Ensure KS in-line connector is disconnected. Measure resistance between KS connector terminal White wire and ground. If resistance is 500-620 k/ohms, replace PCM. If resistance is not 500-620 k/ohms, replace knock sensor.

Dave H
Mar 12, 2010.
Hi Dave H,
Thank you for your quick response, however I am not a mechanic so this is quite confusing to me. Should I have the MAF sensor replaced or should I have them to do all of the stuff below that?

Confused,
Bobbi
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Tiny
Bobbijoscarboro
Mar 12, 2010.
I would have them do the knock sensor test's as you keep getting knock sensor fault codes. But I would also have them check the MAF sensor is working correctly this can only be done using a diagnostic scanner reading live data values. Or you could always try replacing the MAF sensor?

Dave H
Mar 13, 2010.
Actually, while it makes no sense, the water is the problem. I had the EXACT same symptoms and I fashioned a piece of plastic to shield the no1 plug (where my problem was) and it has never occurred again

Tiny
Garrowcustomguitars
Dec 29, 2010.

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